- At least a dozen new subpoenas were authorized Monday by a New Jersey legislative committee investigating a plot by aides to Gov. Chris Christie to create traffic gridlock on the George Washington Bridge, apparently for political retribution.

The panel also agreed to take additional steps to enforce subpoenas on two key figures in the bridge scandal that is engulfing the administration of the Republican governor and possible 2016 presidential candidate.

Former Christie campaign manager Bill Stepien and fired deputy chief of staff Bridget Kelly have asserted their right against self-incrimination and refused to comply with the subpoenas. The panel on Monday voted to reject those objections and continue to seek most of the documents. Four Republicans on the panel abstained, saying they were not given ample time to review the complex Fifth Amendment arguments.

Committee chairman John Wisniewski would not name the new subpoena recipients until they are served, possibly by Tuesday.

The committee's actions follow last week's deadline for 20 people and organizations close to Christie to return subpoenaed documents. All but a few have sought more time. Lawyers for Stepien and Kelly asked that the subpoenas be withdrawn.

"Ultimately, (that is) what the inquiry of the committee is - who knew what when, and who authorized this, and why," Wisniewski said Monday.

The U.S. attorney's office is conducting a parallel criminal investigation.

The traffic jams happened on four mornings in September, when the Port Authority of New York and New Jersey, which runs the George Washington Bridge, blocked two of the three approach lanes from the town of Fort Lee, apparently to punish the town's Democratic mayor. The resulting backups delayed emergency vehicles, school buses and commuters, sometimes for hours.

Five people close to Christie have lost their jobs, including the governor's top two Port Authority appointees, Bill Baroni and David Wildstein. Wildstein, who appears to have overseen the lane closings and is seeking immunity from prosecution, said in a letter last week that "evidence exists" Christie was aware of the lane closings while they were occurring. That's earlier than the governor has said he knew.

The administration has denied Wildstein's claim, made through his lawyer, and has since circulated a memo discrediting Christie's former No. 2 man at the agency.

As the troubles for Christie's administration deepened, other allegations have attracted the attention of federal authorities.

Hoboken Mayor Dawn Zimmer said two Christie Cabinet members told her the city's federal storm recovery aid would be tied to whether she supported a redevelopment project the governor favored. The city on the Hudson River sustained heavy damage from Superstorm Sandy. Christie's office denies the accusations.